#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{/*
	int i = 0;
	int arr[10] = { 0 };
	for (i = 0; i < 4; i++)
	{
		scanf("%d", &arr[i]);
	}

	for (i = 3; i >= 0; i--)
	{
		printf("%d ", arr[i]);
	}
	return 0;
	*/
	double sum = 0;
	int sign = 1;
	int i = 0;
	for (i = 1; i <= 100; i++)
	{
		sum += sign * 1 / (double)i;
			sign = -sign;
	}
	printf("%.3f\n", sum);
	return 0;
}